On the basis of primate studies of cerebral vasospasm we believe that a prospective double blind clinical study of patients with cerebral aneurysm is now in order. During the past year we have shown that the administration of reserpine or kanamycin will completely prevent hemorrhagic vasospasm in monkeys if blood serotonin levels are reduced to low levels. Our studies indicate that hemorrhagic vasospasm is due to platelet amines or other platelet borne agents. Pilot studies in patients have shown that normal doses or oral kanamycin or parenteral reserpine given together will effectively reduce blood serotonin levels. It is proposed that these agents be administered to patients who are to undergo craniotomy for ruptured cerebral aneurysm in an effort to minimize operative vasospasm and infarction. The success or failure of treatment will be judged primarily by the clinical results and postoperative angiography. The study will be conducted in collaboration with the Massachusetts General Hospital, Peter Bent Brighman Hospital, Boston City Hospital and the Lahey Clinic.